Sir, Since u have the alloy as stepney I doubt it wud b much of a hassle as u can simply lift the MDF board the sub is mounted on and fill the air as there is a bigger gap between the spokes as it won't be that hard to access. Sure there will b an issue in filling the air in the stepney(steel rim) but then one has to make some compromises, this seems to be the most awarding compromise.
As for the alloy thing u can remove(cut) the mounting bolt and place it upside down(damp the base so tht the alloy is not damage) and fit the sub in. This doesn't affect the warranty as they hardly notice it so this is one risk u can take.

Even now I am not using the mounting bolt since it is not long enough to fit on the alloy. The alloy sits well in the well and does not bounce around.

I tried inverting the alloy. Damage can be prevented by putting some soft material in the well. But the angle of the nozzle prevents filling air with the steppeny inverted. So, this becomes a major issue.

Anyway, for the time being I am quite happy with the compos - they give a reasonable amount of bass.